Aviation safety investigations & reports

Summary

The pilot of a Turbo Commander reported, that when on short
final approach to runway 29 centre (29C) at Bankstown Airport, he
saw another aircraft, above and slightly to the left of his
aircraft, in close proximity. The pilot of the Turbo Commander
conducted a go around. The other aircraft was subsequently found to
be a Cessna 152 (C152) flown by a pilot conducting circuit training
as part of commercial pilot licence training.

The occurrence happened about 1 minute after evening civil
twilight of 1819 Eastern Standard Time. The Aeronautical
Information Publication defines that period between evening civil
twilight and morning civil twilight as `night'. The Bankstown
automatic terminal information broadcast at the time advised that
runway 29C was available for all operations on radio frequency
132.8 MHz, the wind direction was 270 degrees M at a speed of 15
kts, with a maximum crosswind of 10 kts and the barometric pressure
was 1013 hectopascals.

Due to the onset of twilight, the aerodrome controller (ADC) was
transitioning from multiple runway to single runway operation.
Runway 29C is the preferred runway for night operations. Traffic
disposition at the time was three single-engine aircraft conducting
circuit training, two arriving aircraft and one aircraft ready for
departure.

The ADC instructed the pilot of the Turbo Commander to join left
downwind for runway 29C at 1,500 ft, as the second aircraft in the
arrival sequence. The first aircraft in that sequence was an Aero
Commander 500, also tracking to join left downwind at 1,500 ft.
Both aircraft were operated by the same company. The pilot of the
Turbo Commander requested, and was approved by the ADC, to maintain
2,000 ft until sighting `the other company traffic'. The pilot of
the Turbo Commander reported to the ADC on a wide downwind at 2,000
ft. The ADC instructed the pilot of the Turbo Commander to descend
to 1,000 ft and to follow the company Aero Commander. General
Aviation Aerodrome Procedures (GAAP) require a pilot who is
instructed to follow a particular aircraft, to sight the other
aircraft and to regulate aircraft speed to achieve longitudinal
spacing. Those procedures also require a pilot to report to the ADC
if they are unable to see, or lose sight of, the aircraft. The
pilot of the Turbo Commander requested an update of the position of
the Aero Commander ahead and the ADC advised that it is `in your 10
o'clock'. The pilot acknowledged that advice and continued the
approach.

Pilots of both instrument flight rule (IFR) and visual flight
rule (VFR) category flights operating in a GAAP control zone (CTR)
are required to operate in accordance with the VFR. Also, Civil
Aviation Regulation (CAR) 163A stated, `When weather conditions
permit, the flight crew of an aircraft must, regardless of whether
an operation is conducted under the IFR or the VFR, maintain
vigilance so as to see and avoid other aircraft.'

Within a GAAP CTR, controllers use sequencing instructions
and/or provide traffic information to pilots to assist them to
manoeuvre to avoid other traffic. Other than the application of
runway separation standards between aircraft during take off or
landing, an ADC does not use standards to segregate airborne
aircraft.

Pilots of aircraft operating in a GAAP CTR are not required to
use the aircraft's secondary surveillance radar transponder. The
pilot of the Turbo Commander and the pilot of the Aero Commander
were operating their respective transponders. The pilot of the C152
was not operating that aircraft's transponder. The ADC had access
to a tower situational awareness display (TSAD), to assist in
maintaining situational awareness. The TSAD used radar information
from the Australian Advanced Air Traffic System and provided a
track history, callsign (or mode A) and altitude if the SSR
transponder was operating, and aircraft ground speed. The TSAD was
limited in scale and definition and the display monitor was located
to the rear of the tower console.

Recorded radar data indicated that the Aero Commander and the
Turbo Commander entered the control zone with groundspeeds of 170
kts and 260 kts respectively. The maximum ground speed of the C152
was 110 kts for a short period when mid-downwind. The downwind leg
for the Turbo Commander was laterally displaced about twice the
distance from the runway centreline, compared with the other
aircraft in the circuit, due to the need to descend and also to
maintain spacing with the aircraft ahead. The pilot of the Turbo
Commander reduced the aircraft's groundspeed while tracking via
downwind and base.

The pilot of the C152 reported downwind and was instructed by
the ADC to sight and follow the Turbo Commander on a `late wide
downwind'. The pilot saw that aircraft and also noted another
aircraft on final approach to the runway. Subsquently, the pilot of
the C152 lost sight of the Turbo Commander and on late base
requested an update of the position of that aircraft from the ADC.
As the ADC was responding, the pilot of the C152 saw the Turbo
Commander to his right at an altitude slightly below that of the
C152. At that stage the pilot of the Turbo Commander commenced the
go around and advised the ADC. Recorded radar data showed that just
prior to the go around, the Turbo Commander was 200 m west of the
C152 and on a converging track. The groundspeed of the Turbo
Commander when on final approach was 100 kts; the groundspeed of
the C152 on late base was 70 kts.

While the TSAD was available to assist the ADC, it is unlikely
to have been of much benefit as that controller needed to visually
monitor all aircraft in the circuit. The occurrence reinforces the
need for vigilance by both pilots and controllers during GAAP. The
pilot of the C152 was required to maintain separation with and to
follow the Turbo Commander, but was probably constrained by his
limited flying experience. The ADC, having established an arrival
sequence, was required to monitor the situation to ensure that it
happened as planned. A combination of darkness, the transition to
single runway operations and the significantly higher groundspeed
of the Turbo Commander, compared with the other aircraft in the
circuit at the time, were additional factors that increased the
complexity of the situation.